Projection light unit



J. W. LEGG.

PROJECTION LIGHT UNIT. I APPLICATION FILED MAR. 31, 1915.

1,325,254. Patented Dec.16,1919.

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PROJECTION LIGHT UNIT.

APPLICATION FILED MAR. 31, I915.

1325254.- Patented Dec. 16,1919.

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Pa'fefited Dec. 16, 1919.

3 SHEETS"SHEET 3- v Ever-22 02:

osnrn w. Lnee, or WORCESTER, MASSACHUSETTS.

PROJECTION LIGHT UNIT. I

Application filed March 31;

To all whom it may concern.-

Be it known that I,-Josnrr1 W; Lnoe, a citizen of the United States, residing at Worcester, in the county of Worcester and State of Massachusetts, have invented a new and useful Projection Light Unit, of which the following is a specification.

This invention relates to a high efiiciency incandescent filament gas-filled projection light unit and the principal" objects thereof are to provide a unit especially for this purpose, and also capable of'other uses, in which the principle of the gas-filled lamp now inuse can be employed with a very much increased effectiveness; to provide means whereby with the projection of a relatively great proportion of the light to p p the. desiredpoint, there shall be'a relatively Fig. 3 with one half in horizontal section; 70

small proportion of heat given ofi at the filament so that one of the serious objections to the use of the arc type of lamp is obviated; to provide an arrangement whereby the heated gas around the filament will be conducted away and returned in a'comparatively cool condition and yet it will be kept away from direct contact with the filanfent on its return so as to avoid sudden cooling thereof; to provide simple and effec tivemeans whereby the usual opaque de osit that is produced on the inner walls 0 the globe orcontainer inthis type of lamp will be projected into an external space where the collection of the deposit will notafi'ect the efliciency of the lamp'and to cause the vcurrentof cool gas to spread out along the surfaces of the globe when it returns there-.

to, whereby the wall of the'globeor .con-

- tainer through which the light is proiected can be located comparatively near the filament so that a relatively large proportion of the luminous rays from the filament can be utilized; to provide an improved form of globe or container in which the rays of1ight that. are normally thrown backwardly can be projected forwardly without causing anyinterference of these with the direct light rays; to provide means whereby the filament can if desired be withdrawn and replaced and the lamp refilled with inert gas so' as to permit of running the lamp at a relatively high efliciency at the expense ofthe length of life of the filament; to provide an tight of course;

Specification of Letters Patent. Patented Dec. 16, 1919.

1915'. Serial No. 18,284.

improved lens construction in cooperation with the lamp and its filament; and to provide improvements in various details of con- ,struction' and combinations of parts as will appear.

first two figures, a light unit is shown'in I which the main container or globe is formed. on two sides by a'spherical 'mirror 10 and a meniscus convex lens 11 of hemispherical form.' These are mounted on the sides, of a metal casing 12' which constitutes the supporting means. The mirror'and lens inclo'se a substantially spherical space which forms themain body. of the lamp and is provided with a-high candle power filament 13. of, well known type located at the center of the sphere. This filament preferably is of hi h current consumption and ada ted to e; operated at a reduced voltage or the purposeof permitting the use of a very small concentrated filament of high efiiciency.

,The container or globe is filled with an inert gas such for example asnitrogen. Itmay be filled and emptied through a metal! lic tube 14 adapted to be pinched together and solderedv or welded after thescontainer is filled with gas., i

The filament is provided with terminals I onleadmg in wires 15, which are tapered at the lower 'ends andseparated by an ins'ulation strip ,16 of any desired insulating material. 'They are insulated and driven into a tapered hole ina screw plug-17 which islprovided with a gasket and all made gas N that most of the deposit is made on the in-- ner walls of the to of the annular-space 20.

spherical space.

the gas to rise into the top of the annular space and it is then forced to descend in this space. This allows the gas to cool and upon cooling it descends to the bottom of the With this current of gas it will be seen This largely avoi s the deposit onthe mirror 10 and the inside of the lensll. For the purpose of more fully accomplishingthis result, a deflecting plate 21 is shown of a. material, such as mica, which will guide and deflect the convection currents bnt will transmit radiant heat and light. It is open at the top to provide a space through which the gas and dark particles of the deposit can enter the annular space. But at the bottom it is bent as to provide side passages 22' through which the gas coming in from the annular space will be caused to of these cooler gases and unduly coo ing it. 1

spread outwardly and pass along the surfaces of the lens .and mirror, thus cooling these surfaces andassis ing -inkeeping the deposit away fromth m. It. also has the further efiect of preventing the discharge directly on the filament It will-be noticed that the outer wall of the annular space is corru ated. This is for permitting cooling, an in case it-is made of thin materials, to allow for expansion and contraction. However, it is preferred to make it of cast aluminum or some other metal not easily affected by theair or gases used. In this case the metallic mirror is welded to the bodyof the casing and the lens is. fixed in'by a cement ring 23 or in any other desired manner. It is to be noted also that the metallic mirror is provided with a corrugation at 24 to permit of expansion and contraction without unduly strain in the joint. r

. he lens itself is animportant feature because it is designed to correct itself for spherical aberration. For this purpose its inside surface is a section of a true sphere concentric with the filament and mirror.

Its outside surface is in the form of a comletehemisphere with its center at a definite.

istance'from the filament. This distance, in order to secure the above mentioned result, is made equal' to the quotient of the radius of thehemisphere by the index of refraction of the material of the lens as compared with air. 'The focusing oflthe light rays can be controlled by-moving the light unit as a whole relative to the regular condensing lenses.25 of the projector.

In the form shown, the lens will take a beam at an angle of 50 from the axis and bendfiit to 3.0% from'theaxis and deliver it to an ordinary 4%" diameter condensing lens 25'. This increases the available light substantially 158% over that that would be times the efliciency of the bare filament is heating the container .in any one place.-

However, an ordinary. spherical globe, containing a four-thousand candle-power fila-.

obtained from the bare filament. With the 4 spherical mirror 10 added, considermg it even with the low efficiency of 55%, four obtained for projection urpos'es evenwith.

ment ofthis type would be much too large to sufliciently approach the regular condensing lens. Even if this were possible the bare filament would require 1 nearly fourtimes as much power and would give off nearly four times as much heat. 1 i

n It will 'be understood that'the object 'of .makin the filament renewable is to make it possib e to runthe filament at a higher temperature than is customary. This greatly increases the efiiciency but atthe expense of the lifefof the filament, which would be impractical with a non-renewable filament lamp. This higher temperature obtained by running the filament at a; greater current and voltage permits of the use of a much'more concentrated filament per candle power and a decrease in the. number of watts consumed per candle power. This arrangement is of practical advantage in some cases, as for instance in moving picture houses, because the cost of renewal would be much less than the cost of an equal candle-power-hour consumption of earbons in an are light unit, besidesfurnishqulring no attention.

This unit will operate even more efiiciently on alternating. current circuits'than with direct currents, hence no motor generator or mercury arc rectifier is needed and one of the advantages of this invention is that they can be dispensed with and re laced by a small transformer at a great redilction of expense.

mg a perfectly steady even illumination reemits a great deal of radiant heat energy' iThis light unit emits no less radiant heat energy per candle ower delivered than an ordinary nitrogenled lamp, but it has a much smaller proportion of heat due to the heating of the'gas. It has a great advan-' tage over the are lamp because the latter which excessively heats the lenses and the film or lantern slides.

.can be cooled and returned to the lamp.

' cooled gases along the surfaces of the globe A deflector 21 is shown for directing the 8 and away from the filament 13 The lens 11 is just like the lens llibut is spaced from the globe so as to provide an annular cooling space for the water which surrounds all the parts above described inside the easing 9. This lens is fixed in a holder 26 forming a part of the casing. The ordinary lenses 25, are mounted in a holder 27 which is movable independently of the casing 9*.

I also provide a casing 28 for the lantern slide holder. In this case the filament is not shown as readily renewable but is mounted in a plug 16 at the bottomwhich is provided with a packing 17 29 and rod 30* are shown adjustably mounted in connection with each other, the tube being connected with the casing 9 and the rod with the casing 28? to provide the necessary focusing adjustment. In this case the principles above mentioned, or most of them, are also employed including the corrugation of the tube 20 to provide for contraction and expansion and to some degree toallow radiation for cooling purposes.

Although I have illustrated and described only two forms of my invention, I am aware of the fact that many modifications can be made therein by any person skilled in the art without departing from the scope of the invention as expressed in the claims. There- This unit also fur- 'nishes a perfectly steady, even illum nation which is water tight. A tube main walls of the container, and means below said filament for directing the cooler portion of the current of said gas away from the filament and along thewalls of the container, the last'nained means bein 'capableof transmitting radiant heat and light. 2. A projection unit comprising a container having a filament therein and provided with an opening at the top, and a corrugated longitudinally expansible bypass extending from said opening around to the bottom of the container.

3. A projection unit comprising. a container provided with a substantially spherical body and having a filament located at the center thereof and provided with two semicircular passages extending around said body from the top to the bottom and opening out from the top of the spherical body and into the bottom thereof, whereby heated gas will rise in the top of said container and ,pass around the same in said passages to be cooled and will enter the'bottom of the spherical portion of the container below the filament. 4. A projection unit comprising a containerv rovided with a substantially spherical bo y and having a filament located at the center thereof and provided with two semicircular. assages extending around said body from t e top to the bottom and opening out from the top of-the spherical body and into the bottom thereof, whereby heated gaswill rise in the top of said container and pass around the same in said passages and enter the bottom of the spherical portion of the container below the filament, and a deflector ofheat resisting material within the container passing around the sides thereof and across the bottom, the bottom being flattened to permit the entrance of the cooled gas along the. side walls-\of the container 1 and the top being open to permit the escape of the heated gas into said passages.

5. A' projection unit comprising a. container provided with a body'havin a filament and provided with a semi-circu ar passage extending around said body from the top to the bottom, whereby the heated gas will rise in the top of said container and pass around'the same in said passage and enter the bottom of the spherical portion of fore, I do not wish to be limited 'to all the -the container below the filament, and a dethrough of any deposit from the filament,

means for creating a current of the gas through said opening to facilitate the deposit ofparticles through said opening for, .the purpose of-keeping it away from theflector of non-conducting material within 'the container passing around the sides thereof and across the bottom, the bottom being bent to permit the entrance of the cooled gas along the sidewalls of the container and the top being open to permit the escape of the heated gases into said passage.

6. A projection unit comprising a metallic casing of a general clrcular form provided with an annular passage around the exterior thereof and having inside said casinlg but at the'opposite sides thereof respectively a" spherical mirror and a spherical lens sub-- stantially concentric with each other, said .lens andmirroiz' v V In testimony whereof I have hereunto set openings at the bottom for discharging the cooled gas 'along the walls of the mirror and at the center of the lens, and a filament my-handn e JOSEPH W. LEGG. 

